Investigating Plastic Contamination in Olive Oil with GC–MS/MS

A recent joint study between NOVA University Lisbon (Caparica, Portugal) and the University of Évora (Évora, Portugal) monitored the contamination of 23 phthalates and 9 phthalate substitutes in olive oil throughout the production and storage process. Analysis conducted using gas chromatography tandem mass spectrometry (GC–MS/MS) revealed that plasticizer concentrations progressively increased at each stage of the production process, although unprocessed olives also contained contaminants. A paper based on the study was published in Molecules (1).

Rich in antioxidants such as phenols and tocopherols, olive oil is a staple in the Mediterranean diet and is consumed at a rate of approximately three million tons per year worldwide (2,3). The materials initially used in the production and storage of olive oil included wood, glass, metal, and clay; however, industrial evolution has led to the use of polymers such as polyethylene and polypropylene, especially in the packaging process, because of their advantages in cost, recyclability, and durability (4-8). The increasing need for versatility of polymers has led to the development of additives to enhance their properties. Among these additives are phthalates, which are used to make the material more flexible or rigid, depending on the need. Phthalates are widely used in the food and engineering industries in products ranging from food packaging to pipes, tubes, and mats (9–12). Despite the benefits phthalates offer for the durability and functionality of polymers, they have low solubility in water and high solubility in lipid matrices, such as olive oil, which may result in their migration into food products (10,11).

The authors of the study report that the optimized analytical method used for quantification demonstrated adequate performance in terms of detection limits and excellent repeatability while requiring relatively small solvent volumes and ensuring effective sample clean-up. Analyses conducted throughout the production line revealed a progressive increase in plasticizer concentrations, having identified olive harvesting and industrial processes as predominant contamination sources, along with storage, particularly in polyethylene terephthalate (PET) packaging, over long periods (1).

Among the compounds analyzed, diisononyl phthalate (DINP) was the most common, with an average concentration of 3.387 mg/kg and a maximum value of 9.393 mg/kg in oils stored in both glass and PET. These results indicate that some stored oils exceeded the specific migration limits established by European regulations (1.8 mg/kg). The significant presence of DINP, as opposed to plasticizers such as bis(2-ethylhexyl) phthalate (DEHP), reflects the gradual replacement of the latter in industrial applications and highlights the growing prevalence of DINP in construction materials, industrial machinery, and ecosystems (1).

Although the total concentration of plasticizers analyzed did not exceed the limit set by European regulations (60 mg/kg), the authors note that this study covered only 32 compounds, and many other plasticizers are currently in use. Furthermore, given the importance of olive oil as a widely consumed food product, they believe that it is essential to precisely identify contamination sources and implement effective mitigation strategies. While replacing plastic materials with safer alternatives such as stainless steel or adopting phthalate-free plastics are fundamental measures, it is equally crucial to monitor and evaluate these materials, as even those labeled as phthalate-free may release contaminants over time because of mechanical stress and temperature. Additionally, new phthalate replacement plasticizers must be monitored and toxicologically tested. The authors believe that accurate diagnostics and the implementation of mitigation strategies will significantly reduce plasticizer contamination, ensuring greater consumer safety and preserving the quality of this essential food product (1).

Olive oil and olives on a wooden table under an olive tree. © volff - stock.adobe.com

References

1. Freitas, F.; Brinco, J.; Cabrita, M. J.; Gomes da Silva, M. Analysis of Plasticizer Contamination Throughout Olive Oil Production. Molecules 2024, 29 (24), 6013. DOI: 10.3390/molecules29246013

2. Davis, C.; Bryan, J.; Hodgson, J.; Murphy, K. Definition of the Mediterranean Diet; a Literature Review. Nutrients 2015, 7 (11), 9139–9153. DOI: 10.3390/nu7115459

3. Global Consumption of Olive Oil 2022/23. Statista website.https://www.statista.com/statistics/940491/olive-oil-consumption-worldwide/ (accessed on 2024-10-30).

4. Marsh, K.; Bugusu, B. Food Packaging--Roles, Materials, and Environmental Issues. J. Food Sci. 2007, 72 (3), R39–55. DOI: 10.1111/j.1750-3841.2007.00301.x

5. Mangaraj, S.; Goswami, T. K.; Mahajan, P. V. Applications of Plastic Films for Modified Atmosphere Packaging of Fruits and Vegetables: A Review. Food Eng. Rev. 2009, 1, 133–158. DOI: 10.1007/s12393-009-9007-3

6. Kirwan, M. J.; McDowell, D.; Coles, R. Food Packaging Technology; Blackwell, 2003.

7. Thompson, R. C.; Moore, C. J.; Saal, F. S. V.; Swan, S. H. Plastics, the Environment and Human Health: Current Consensus and Future Trends. Philos. Trans. R. Soc. B Biol. Sci. 2009, 364, 2153–2166. DOI: 10.1098/rstb.2009.0053

8. Andrady, A. L.; Neal, M. A. Applications and Societal Benefits of Plastics. Philos. Trans. R. Soc. B: Biol. Sci. 2009, 364, 1977–1984. DOI: 10.1098/rstb.2008.0304

9. Staples, C. Phthalate Esters; Springer-Verlag, 2003.

10. Heudorf, U.; Mersch-Sundermann, V.; Angerer, J. Phthalates: Toxicology and Exposure. Int. J. Hyg. Environ. Health 2007, 210, 623–634. DOI: 10.1016/j.ijheh.2007.07.011

11. Alamri, M.S.; Qasem, A.A.A.; Mohamed, A.A.; et al. Food Packaging’s Materials: A Food Safety Perspective. Saudi J. Biol. Sci. 2021, 28, 4490–4499. DOI: 10.1016/j.sjbs.2021.04.047

12. Craver, C.; Carraher, C. Applied Polymer Science: 21st Century; Elsevier B.V., 2000.